1996 Volume 105 Issue 1 Pages 1-14
Chemical studies of the stream water in a small forested watershed were conducted at Aidzu-Tajima, Fukushima prefecture. The experimental watershed is located under the snowy temperate climate, and has an area of 0.14 km2. The bedrock of the watershed consists of consolidated sediment formed in the Neogene. The watershed is entirely covered with forest vegetation. Maximum monthly precipitation is observed in summer however, maximum monthly runoff is recorded in snowmelt season. The HCO3- concentration of stream water is diluted by snow meltwater, and episodic increase of concentrations of Cl-, NO3- and SO24- is observed during the snowmelt season. The pH of stream water is lower during the snowmelt season than summer and autumn. The ionic composition of stream water is variable according to the seasons. Bicarbonate is the major anion in summer, and the ratio of Cl-+NO3-+SO24- increases in snowmelt season. The factor analysis is applied to the data matrix of chemistry of stream water. In the winter season, the explained variance of factor 1 which relates to acidity of stream water is 38.7 %, and the explained variance of factor 2 which relates to sea water origin is 28.4 %. Two thirds of variation of stream chemistry is explained by the chemical factor released from snowcover by melting.
